Inflatable air cells have been used in a variety of configurations in the lumbar region of a seat to provide adjustments to the contour of a seat and in this manner enhance the comfort of the individual using the seat. This is especially important in automobiles where long periods of driving can cause pain and distraction or in other seating applications where individuals are sedentary for long periods of time.
The seating system described in U.S. Pat. No. 4,915,124 involves a simple system of multiple air cells in which each cell is connected through a valve to a source of pressurized air in a manner which allows for simultaneous inflation or deflation of the cells in response to a manually operated switch.
Another air cell inflation system is shown in U.S. Pat. No. 5,263,765. This device inflates the air cells according to two predetermined modes, through tubes individually controlled by valves which are in turn controlled by a microcomputer. The microcomputer is responsive to the fatigue of the driver as represented by seat belt displacement.
The air cells of U.S. Pat. No. 4,722,550 are adjusted in response to engine speed or steering angle and allows for selective inflation between two zones of air cells, one at the sides and one for the bottom and back of the seat. One valve controls each of the zones and is actuated by a microcomputer which receives sensed signals relative to the operating parameters of the automobile.
A manually operated power control system for a lumbar cushion is described in U.S. Pat. No. 4,707,027. A complex seating mechanism is devised to allow the operator to inflate and deflate the cushion while sensing pressure in the cushion to limit actuation of the system to prevent damage.
U.S. Pat. No. 4,833,614 shows a system by which an air cell can be inflated to a selected pressure by sensing the actual pressure, comparing it to the pressure selected and then adjusting the air supply to inflate or deflate the air cell to the selected pressure. In this case the microcomputer converts the pressure signal it receives to a time based signal relative to the period necessary to run the pump to obtain the selected pressure. The pressure is sensed directly from sensors within the air support.
U.S. Pat. No. 4,655,505, assigned to NHK Spring Co. Ltd., discloses a pneumatically controlled seat for a vehicle that has a mechanism which can sense the pressure in each air cell remotely in a manifold using one sensor.
The above systems are limited either to narrow preset operational boundaries or rely on the operator to provide a manual interactive response and they do not provide an arrangement in which the lumbar air cells can be separately adjusted to provide a tilt support to a user's back in the vicinity of the lumbar air cells. Although each attempts to improve the comfort of the user and adjust in some manner to the variety of shapes and sizes of the user, each falls short because of the inherent limitations in the particular system.
Another air cell adjustment mechanism of the prior art is shown in U.S. Pat. No. 5,137,329. This patent describes a support structure consisting of front and back plates between which are sandwiched two air cells. The air cells may be selectively inflated and deflated to provide pivoting adjustment motion to the front plate which provides the support contour for the seat.
Tactile adjustment is provided by the air cell of U.S. Pat. No. 4,807,931 which is also mounted in a seat to provide the support contour for directly engaging the lumbar region of the user's back.
However, such prior art does not utilize the positioning of lumbar air cells to provide a tilt adjustment of a lumbar support for adjusting it to a wide variety of users.